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Lab test

Alkaline Phosphatase, Bone Specific Test

This test measures bone-specific alkaline phosphatase, or BSAP, in a blood serum sample. It is described as a general index of bone formation and a specific index of osteoblast activity.

Quest patient service center

About this test

Bone-specific alkaline phosphatase, or BSAP, is an enzyme associated with osteoblasts, the cells responsible for forming new bone. Quest describes BSAP as a general index of bone formation and a specific index of total osteoblast activity, and lists the test under several names, including OSTASE, BSAP, and Alkaline Phosphatase, skeletal.

Quest describes BSAP as one of the most effective markers of bone formation, and notes it is used for monitoring bone formation therapies and antiresorptive therapies. The sample is a 1 mL serum specimen, analyzed using immunoassay.

Test details

CollectionQuest patient service center

Quest resources

Additional details

What this test looks at

The test reports a single value: the level of bone-specific alkaline phosphatase in serum. Quest lists it under several names, including OSTASE, BSAP, and Alkaline Phosphatase, skeletal, which all refer to the same measurement.

This test isn't part of the Celio Health store at the moment, so it can't be ordered or requested here. The test menu lists everything that can.

Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.

Frequently asked questions

What does this test measure?

It measures bone-specific alkaline phosphatase (BSAP), an enzyme Quest describes as a general index of bone formation and a specific index of total osteoblast activity.

How is the sample collected?

The test uses a 1 mL serum sample analyzed by immunoassay.

Do I need to prepare for this test?

No preparation instructions are listed for this test, though people follow any instructions their ordering clinician provides.

What is this test used to monitor?

Quest describes BSAP as used for monitoring bone formation therapies and antiresorptive therapies.

Last updated 2026-09-18 · How we write about lab testing

Educational content

This page is for general educational purposes only. It is not medical advice, and it is not a substitute for consultation with a qualified healthcare professional. Laboratory results should always be interpreted by a licensed clinician who knows your health history. If you have questions about your health or your results, talk with your doctor. If you think you may be experiencing a medical emergency, call 911.